Recently, large capacity information recording mediums represented by DVD discs have been developed. Conventional CDs (compact discs) have a recording capacity of 650 MB, whereas DVD discs have a recording capacity of 4.7 GB on one surface. Currently, higher density information recording mediums using blue laser have been developed. This allows a higher quality content to be recorded on one information recording medium for a longer time than in a CD. For example, one CD allows a music content of 44.1 kHz/16 bits/2 ch to be recorded thereon for about 74 minutes. A DVD-Audio disc allows a content of a maximum of 192 kHz/24 bits/2 ch or a maximum of 96 kHz/24 bits/6 ch to be recorded thereon for about the same length of time. A DVD-Audio disc allows a music content of 44.1 kHz/16 bits/2 ch to be recorded thereon for about 6 times longer than a CD. (See, for example, DVD Specifications for Read-only Disc, Part 4, AUDIO SPECIFICATIONS Version 1.2.)
Recently, various types of compression recording systems represented by mp3 have been invented, and a music content is recorded using such compression recording systems. In the case where, for example, a 5-minute tune is recorded using 128 kbps mp3, the data amount is about 5 MB. When a 5-minute tune is recorded on a CD (44.1 kHz/16 bits/2 ch), the data amount is about 50 MB. The data amount recorded using 128 kbps mp3 is only ⅕ of the data amount recorded on a CD.
In order to prevent a content from being illegally copied, the content is recorded on an information recording medium in the state of being encrypted. A music content recorded on, for example, a DVD-Audio disc is encrypted using a certain encryption technology. In the case where a copyright management information regarding the copyright of the encrypted music content is recorded on the information recording medium, the copyright indicated by the copyright management information can be applied when copying the music content. In the case where, for example, the copyright management information indicates that the content is permitted to be copied only once, the content is controlled to be permitted to be copied once and not to be permitted to be copied anymore. It is possible to record such copyright management information as to completely prohibit the content from being copied.
A label gate CD has contents recorded thereon as follows. One label gate CD is divided into two sessions. In one session, a music content treated with CCCD (Copy Control CD) is recorded. CCCD is a copy protection technology, and a content treated with CCCD is unreadable by a usual CD-ROM drive. In the other session, a music content to be reproduced using a CD-ROM drive is recorded. In this case, a usual CD reproduction apparatus reproduces the music content treated with CCCD, and a personal computer reproduces the music content to be reproduced by the CD-ROM drive. However, the label gate CD does not have information recorded which indicates the relationship between the two types of music contents recorded in the two sessions. Accordingly, the music contents recorded in the two sessions cannot be handled differently in accordance with the reproduction conditions, copying conditions or the like. In addition, a personal computer cannot read the music content treated with CCCD, and thus cannot controllably reproduce or copy such a music content.
A DVD-Audio disc can allow a high quality music content to be recorded thereon. Therefore, a music company which creates a music content to be recorded on DVD-Audio discs may desire that such a high quality music content should not be copied. However, users listening to the content of the DVD-Audio discs desire to copy the music content recorded on the DVD-Audio discs for his/her personal use.
There is another problem as follows. Even if a high quality music content recorded on the DVD-Audio discs is permitted to be copied, it is time-consuming to copy the content due to a large data amount of the content. For example, a 5-minute tune recorded on a CD (44.1 kHz/16 bits/2 ch) has a data amount of about 50 MB, whereas a 5-minute tune recorded on a DVD-Audio disc (44.1 kHz/24 bits/6 ch) has a data amount of about 240 MB. Therefore, it takes about five times longer to copy the music content recorded on a DVD-Audio disc than to copy the music content recorded on a CD.
When reproducing a music content using a portable reproduction apparatus, there is a general problem of power consumption. Portable reproduction apparatuses are driven by storage cells. When reproduction of data requires a larger power consumption, the time in which the data can be reproduced is shorter. The high quality music content recorded on a DVD-Audio disc has a large data amount. When the data amount of the music content is significantly larger than the memory capacity of a portable reproduction apparatus, it is impossible to store all the data of the music content in the memory of the portable reproduction apparatus before reproduction. Therefore, the DVD-Audio disc needs to be rotated to have the data read therefrom while the data is being reproduced by the portable reproduction apparatus. The power for rotating the DVD-Audio disc is required, which makes long-time reproduction difficult.